What is a coolant flush?

The engine cooling system is made up of a set of components connected in a closed loop to circulate engine coolant through the engine, and maintain the coolant at a constant temperature. Coolant can degrade over time, and eventually requires replacement to protect the cooling system from corrosion. Cooling system corrosion can result in leaks, and debris accumulation which can result in restricted coolant flow; both of which can lead to engine overheating.

How does coolant work?

As the engine runs combustion events occur thousands of times per minute; heat is a byproduct of engine operation. To prevent that heat from destroying the engine, a liquid cooling system is used. Beginning with the engine, the cooling system uses coolant passages inside the engine block, cylinder head, and possibly the intake manifold. These passages allow coolant to flow through these components to absorb heat.

The water pump pushes the coolant through the thermostat and into the radiator, where it is cooled, then returned to the engine for another cycle. The thermostat regulates the temperature as engine coolant will not move past the thermostat unless the set temperature has been reached. Since this is a pressurized system with no air, the engine coolant can reach extreme temperatures without boiling off as steam.

What symptoms may require a coolant flush?

Not changing the coolant in your vehicle on a regular basis may affect engine performance. So, it's important to have it serviced routinely as part of factory scheduled maintenance. If the coolant has not been flushed regularly, you may experience one of more of these symptoms:

Can I drive without a coolant problem?

If engine coolant is being flushed as part of factory scheduled maintenance, with no other symptoms, driving the vehicle should pose no more problems than normal. However, driving a vehicle with a faulty engine cooling system can result in overheating, cylinder head gasket failure, engine block failure, or cylinder head warping. It is never recommended to drive a vehicle with engine cooling issues, especially with modern engine casting materials.

How often should the coolant be flushed?

On older vehicles it is often recommended to flush the engines cooling system every two years or 30,000 miles, many newer vehicles have extended life coolant which can last up to 100,000 miles. To be safest, it's always recommended to follow the service intervals found in the owner's manual. Each manufacturer protects their customer by testing, and specifying when certain preventive maintenance items should be completed. Following the required services listed will help ensure the longevity of the cooling system, as well as the rest of the vehicle.

Outside of routine maintenance, coolant may need to be drained and replaced as part of a cooling system leak. In that case, a full coolant flush should be performed if excessive corrosion is present, or if the factory scheduled service interval has already been surpassed.

How are coolant flush issues diagnosed?

Coolant changes normally do not require a diagnosis. They are most often completed as scheduled maintenance, or as part of a repair necessitating draining the engine coolant. However, if an engine is exceptionally dirty, or the scheduled maintenance has been missed, the technician will recommend a full cooling system flush and inspection.

How is a coolant flush performed?

Changing the coolant, which is a separate activity from a coolant flush, is done by simply draining the coolant from the radiator, refilling the engine coolant through the reservoir, and running the vehicle until it is full, and free of air.

A coolant flush is much the same, but differs in that there is normally a chemical treatment additive circulated through the engine before draining the coolant. The next step in a flush is to run water into the entire cooling system, flushing out the chemical treatment, corrosion, and old engine coolant.

Then, the radiator and engine block, if equipped with a drain plug, will be drained completely. Once drained, the coolant reservoir is cleaned thoroughly, and replaced. Finally, the engine cooling system will be refilled, and bled of air.

Other coolant flush considerations

Engine coolant flushes are one of the most common services needlessly recommended, raising repair costs. However, there is a schedule for when these services should be performed. The factory scheduled maintenance section in the owner’s manual provides information for the customer concerning which maintenance items should be performed, and when they are needed.

What to be aware of with coolant flush services

There are many brands and types of coolant and engine flushing chemicals available to consumers. Many manufacturers supply a proprietary type that is designed to protect the specific materials used in the construction of the engine cooling system. They may also indicate optional recommended brands. These recommendations should be followed to help ensure the longevity of the cooling system.

Can I perform a coolant flush myself?

The average DIYer can maintain the engine cooling system without much trouble. However, diagnosing the system when problems arise can be a daunting task if the function of each individual component is not fully understood. Flushing the engine cooling system as a DIY is generally safe for the moderately experienced DIYer. If cooling system issues develop after the coolant is replaced, and a good knowledge of the engine cooling system or diagnosing cooling issues are lacking, this repair should be handed to a certified technician.